Have you ever done a UOA?

 

I did a couple of analyses on the truck when it still had all the stock emissions equipment in tact (the first 20K miles on the truck) and one more with the first oil change after removing the emissions equipment. The first couple showed all the indicated markers of a 6.7L having the life choked out of it by the emissions equipment, but the 1 analysis I sent in after 10K miles of being emissions free showed everything was still in the green. I've also performed periodic analyses on my '01 (which has 365K miles), my father's '05 (175K miles) and my uncle's '06 (280K miles), all 3 of which also use the Wix 51607 exclusively, and they have always come back with normal results. My father changes his oil and filter every 5K miles while my uncle changes his oil and filter every 10K miles.

I think it should also be noted what type of oil has been used. On my '08, I was running Amsoil CJ-4 5w40 when all the emissions equipment was on the truck (after the initial couple of oil changes in which I used Delo conventional for break-in) and have been running Amsoil CI-4 20w50 and now 15w40 since removing the emissions equipment. Both my father and uncle have used Mobil 1 full synthetic (not sure which weight they use) since day one. I also run Mobil 1 15w50 in my '01.

Im sure there are better oil filters out there. However, the Wix filters are priced competitively and are always in stock at our local oil change shop so they are what we use. Since none of us run extended drain intervals, I don't see any reason to use any other.

 

Napa Gold/Wix 7620 (standard media) or 7620XE (synthetic media) for me. No problems.
7620:

7620XE: